Fully substituted cyclopolysiloxanes and their use for making organosilicon polymers

ABSTRACT

Disclosed are organosilicon crosslinked polymers and crosslinkable prepolymers that are the reaction product of (a) a cyclic polysiloxane in which each silicon atom is substituted with (i) a saturated, substituted or unsubstituted alkyl or alkoxy group or a substituted or unsubstituted aryl or aryloxy group, and (ii) a substituted or unsubstituted hydrocarbon group having at least one carbon-carbon double bond that is reactive in hydrosilation, (b) at least one organosilicon compound having at least two .tbd.SiH groups, and optionally (c) a hydrocarbon polyene having at least two nonaromatic carbon-carbon double bonds that are reactive in hydrosilation. A process for preparing the polymers and prepolymers and for preparing the cyclic polysiloxanes is also disclosed.

This application is a continuation, division of application Ser. No.08/049,097, filed Apr. 19, 1993 now U.S. Pat. No. 5,334,688.

FIELD OF THE INVENTION

This invention relates to the preparation of organosilicon polymers andprepolymers from cyclic polysiloxanes. This invention also relates tothe preparation of cyclic polysiloxanes.

BACKGROUND OF THE INVENTION

Leibfried, in U.S. Pat. Nos. 4,900,779, 4,902,731 and 5,013,809, andBard and Burnier in U.S. Pat. Nos. 5,008,360 and 5,068,303, describecrosslinked organosilicon polymers and crosslinkable organosiliconprepolymers comprising alternating polycyclic hydrocarbon residues andcyclic polysiloxane or siloxysilane residues linked throughcarbon-to-silicon bonds. These polymers are useful, for example, instructural and electronic applications.

Although cyclic trisiloxanes were disclosed for use in the preparationof organosilicon polymers and prepolymers in U.S. Pat. 5,013,809(Leibfried) and in Research Disclosure 326103 (June, 1991), these cyclictrisiloxanes were required to have two or more hydrogen atoms bound tosilicon. Only cyclosiloxanes containing four or more silicon atoms wereused in the preparation of these polymers and prepolymers, becausecyclotrisiloxanes are not readily available and are unstable. It is alsoknown that cyclotrisiloxanes with hydrogen atoms and methyl groupsbonded to every silicon atom are not storage-stable.

Cyclopolysiloxanes in which some of the Si atoms are substituted withunsaturated polycyclic groups have been disclosed in U.S. Pat. No.4,599,440, e.g., the reaction product of pentamethylcyclotrisiloxane and5-ethylidenebicyclo(2,2,1)hept-2-ene. None of these compounds haveunsaturated hydrocarbon groups on every silicon atom.

SUMMARY OF THE INVENTION

The organosilicon crosslinked polymers or crosslinkable prepolymers ofthis invention are the hydrosilation reaction product of:

(a) a cyclic polysiloxane having the formula: ##STR1## where R is asaturated, substituted or unsubstituted alkyl or alkoxy group or asubstituted or unsubstituted aryl or aryloxy group, R' is a substitutedor unsubstituted hydrocarbon group having at least one nonaromaticcarbon-carbon double bond that is reactive in hydrosilation, and n is 3,or 3 and 4, and

(b) at least one organosilicon compound having at least two.tbd.SiHgroups selected from the group consisting of (1) cyclic polysiloxanesand (2) tetrahedral siloxysilanes.

The reaction mixture can optionally contain as a third component (c) atleast one hydrocarbon polyene having at least two nonaromaticcarbon-carbon double bonds that are reactive in hydrosilation.

The present invention also discloses a method for preparingfully-substituted cyclic polysiloxanes, and processes for preparingprepolymers and polymers from the fully-substituted cyclicpolysiloxanes, other organosilicon compounds, and, optionally, apolycyclic polyene.

The organosilicon polymers of this invention have improved shear modulusand coefficient of thermal expansion compared with polymers made withoutthe fully-substituted cyclic polysiloxanes. The invention also providesa simple method for preparing storage-stable cyclic polysiloxanes.

DETAILED DESCRIPTION OF THE INVENTION

The fully-substituted cyclic polysiloxanes used as component (a) in thepreparation of the organosilicon polymers and prepolymers of thisinvention have the general formula: ##STR2## where R and R' are definedbelow and n=3, or 3 and 4. The notation "3 and 4 " means that a mixtureof a cyclic trisiloxane (n=3) and a cyclic tetrasiloxane (n=4) is used.

The fully-substituted cyclic polysiloxanes are prepared by firstreacting a dichlorosilane having the formula Cl₂ HSiR in which R is asaturated, substituted or unsubstituted alkyl or alkoxy group or asubstituted or unsubstituted aryl or aryloxy group, with a substitutedor unsubstituted hydrocarbon polyene having at least two nonaromaticcarbon-carbon double bonds that are reactive in hydrosilation. The alkylgroups are preferably 1-10 carbon alkyl groups and the aryl groups arepreferably 6-10 carbon aryl groups. The alkyl or aryl groups of thedichlorosilane, or the hydrocarbon polyene, can be substituted with anysubstituents that do not interfere with subsequent hydrosilationreactions. Examples of suitable hydrocarbon polyenes include polycyclicpolyenes such as, for example, cyclopentadiene oligomers (e.g.,dicyclopentadiene, tricyclopentadiene and tetracyclopentadiene),bicycloheptadiene (also known as norbornadiene) and its Diels-Alderoligomers with cyclopentadiene (e.g., dimethanohexahydronaphthalene),norbornadiene dimer, hexahydronaphthalene, and substituted derivativesof any of these, e.g., methyldicyclopentadiene. Other hydrocarbonpolyenes such as those containing a single carbocyclic ring, e.g.,divinylbenzene and divinylcyclohexane, or an acyclic polyene such asisoprene can also be used. The preferred hydrocarbon polyenes aredicyclopentadiene (DCPD) and norbornadiene.

The reaction of the dichlorosilane and the hydrocarbon polyene iscarried out in the presence of a hydrosilation catalyst. Hydrosilationcatalysts include those compounds discussed below in relation to thepreparation of organosilicon polymers and prepolymers. In this reactionone of the carbon-carbon double bonds of the hydrocarbon polyene reactswith the .tbd.SiH group of the dichlorosilane, and the remaining doublebond is unreacted.

The product of this hydrosilation reaction is RCl₂ SiR', where R' is asubstituted or unsubstituted hydrocarbon group having at least onenonaromatic carbon-carbon double bond that is reactive in hydrosilation,which is derived from the hydrocarbon polyene. RCl₂ SiR' is thencyclized by one of three methods to produce the cyclic polysiloxanes ofthis invention: (1) direct hydrolysis, for example, in ether or methylethyl ketone, (2) reaction with a secondary or tertiary alcohol and (3)oxidation with a metal oxide.

Method (1) is preferred for cyclizing RCl₂ SiR' compounds where R' isderived from dicyclopentadiene.

Suitable tertiary alcohols for use in method (2) include, for example,2-methylbutan-2-ol, 3-methylpentan-3ol, 3-ethylpentan-3-ol and t-butylalcohol. Suitable secondary alcohols include, for example, 2-propanol,2-butanol, 2-pentanol, 3-pentanol and 3,3-dimethylbutan-2-ol. Tertiaryalcohols are preferred. t-Butyl alcohol is most preferred.

Metal oxides preferred for use in method (3) include, for example, ZnO,MgO and CuO. Zinc oxide is most preferred. Reaction with ZnO ispreferred for RCl₂ SiR' compounds where R' is derived fromnorbornadiene, and for compounds where R is an alkoxy or aryloxy group.

The preparation of the fully substituted cyclic polysiloxanes can besummarized as follows, using the pure cyclic trisiloxane as an example.

RSiHCl₂ +hydrocarbon polyene→RCl₂ SiR'→ ##STR3## where R is a saturated,substituted or unsubstituted alkyl or alkoxy group or a substituted orunsubstituted aryl or aryloxy group, and R' is a substituted orunsubstituted hydrocarbon group having at least one nonaromaticcarbon-carbon double bond that is reactive in hydrosilation.

Pure cyclic trisiloxane can be obtained by standard processingtechniques. However, 10% to 46% of the cyclic tetrasiloxane having theformula: ##STR4## where R and R' are the same as above, is typicallyalso present in the cyclic polysiloxane reaction product. The amount ofthe cyclic tetrasiloxane present depends upon the synthesis method,reaction conditions and solvent used and on the size of the groups R andR' in the molecule. For example, when R' is derived fromdicyclopentadiene, a smaller percentage of the cyclic tetrasiloxane ispresent when RCl₂ SiR' is reacted with t-butyl alcohol than when RCl₂SiR' is hydrolyzed in methyl ethyl ketone. When RCl₂ SiR' is reactedwith ZnO, a smaller percentage of the cyclic tetrasiloxane is obtainedwhen R' is derived from dicyclopentadiene than when R' is derived fromnorbornadiene. The mixture of the cyclic trisiloxane and the cyclictetrasiloxane can also be used in preparing the polymers and prepolymersof this invention.

Any cyclic polysiloxane or tetrahedral siloxysilane with two or morehydrogen atoms bound to silicon can be used as component (b) in thepreparation of the organosilicon polymers or prepolymers of thisinvention. The cyclic polysiloxanes have the general formula: ##STR5##wherein R² is hydrogen, a saturated, substituted or unsubstituted alkylor alkoxy group, a substituted or unsubstituted aryl or aryloxy group, nis an integer from 2 to 20, and R² is hydrogen on at least two of thesilicon atoms in the molecule.

Suitable cyclic polysiloxane compounds include those disclosed in U.S.Pat. No. 4,900,779; 4,902,731; 5,013,809; 5,077,134; 5,008,360;5,068,303; and 5,025,048, all of which are incorporated by reference intheir entirety. Examples of reactants of Formula (I) include, forexample, trimethylcyclotrisiloxane, tetraoctylcyclotetrasiloxane, andhexamethylcyclotetrasiloxane; tetra- and pentamethylcyclotetrasiloxanes;tetra-, penta-, hexa- and heptamethylcyclopentasiloxanes; tetra-, penta-and hexamethylcyclohexasiloxanes, tetraethylcyclotetrasiloxanes andtetraphenylcyclotetrasiloxanes.

Preferred cyclic polysiloxanes are the methylhydrocyclosiloxanes, forexample, 1,3,5,7-tetramethylcyclotetrasiloxane;1,3,5,7,9-pentamethylcyclopentasiloxane and1,3,5,6,9,11-hexamethylcyclohexasiloxane, or mixtures thereof. In mostcases, a mixture of a number of these species is used, wherein n canvary widely. Reference to "methylhydrocyclosiloxanes" is intended torefer to such mixtures.

The tetrahedral siloxysilanes are represented by the structural formula:##STR6## wherein R² is as defined above and is hydrogen on at least twoof the silicon atoms in the molecule.

Examples of reactants of Formula (II) include, e.g.,tetrakisdimethylsiloxysilane, tetrakisdiphenylsiloxysilane, andtetrakisdiethylsiloxysilane. Tetrakisdimethylsiloxysilane is the bestknown and preferred species in this group.

The hydrocarbon polyenes that can be used as optional component (c) inpreparing the polymers and prepolymers of this invention are hydrocarbonpolyenes having at least two nonaromatic carbon-carbon double bonds thatare reactive in hydrosilation. Preferably the polyenes are polycyclicpolyenes where the double bonds are in the rings of the compounds.Suitable compounds include for example, cyclopentadiene oligomers (e.g.,dicyclopentadiene, tricyclopentadiene and tetracyclopentadiene),norbornadiene dimer, bicycloheptadiene (i.e., norbornadiene) and itsDiels-Alder oligomers with cyclopentadiene (e.g.,dimethanohexahydronaphthalene), and substituted derivatives of any ofthese, e.g., methyldicyclopentadiene. Preferred are cyclopentadieneoligomers such as dicyclopentadiene and tricyclopentadiene, withdicyclopentadiene being most preferred. Two or more hydrocarbon polyenescan be used in combination.

Other hydrocarbon compounds can also be used. For instance, according toone embodiment described in U.S. Pat. No. 5,008,360, which isincorporated by reference in its entirety, the hydrocarbon componentcomprises at least one low molecular weight (typically having amolecular weight less than 1,000, preferably less than 500) polyenehaving at least two nonaromatic carbon-carbon double bonds highlyreactive in hydrosilation. The polyene can contain other less reactive(including unreactive) double-bonds, provided that those double bonds donot interfere with the reactivity of the highly reactive double bonds.Compounds having only two highly reactive double bonds are preferred.The carbon-carbon double bonds can be either in an alpha, beta or gammaposition on a linear carbon moiety, next to two bridgehead positions ina strained polycyclic aliphatic ring structure, or in a cyclobutenering. Examples include 5-vinyl-2-norbornene; o-, m- orp-diisopropenylbenzene; o-, m- or p-divinylbenzene, diallyl ether,diallylbenzene, dimethanohexahydronaphthalene and the symmetrical isomerof tricyclopentadiene.

The reactions for forming the organosilicon polymers and prepolymers ofthis invention are described in U.S. Pat. Nos. 4,900,779; 4,902,731;5,013,809; 5,077,134; 5,008,360; 5,068,303; 5,025,048; and 4,877,820,each of which is incorporated by reference in its entirety.

When components (a) and (b), or (a), (b) and (c) are used to prepare thepolymer or prepolymer, a mixture of all the components can be reacted inthe presence of a catalyst. Alternatively, component (b), the siliconcompound having at least two .tbd.SiH groups, and (c), the hydrocarbonpolyene, are reacted in the presence of a catalyst to form anintermediate product, and the intermediate product is then reacted with(a), the fully substituted cyclic polysiloxane, in the presence ofadditional catalyst. Alternatively (a) the fully substituted cyclicpolysiloxane and (b) the silicon compound having at least two .tbd.SiHgroups, are reacted in the presence of a catalyst to form anintermediate product, and the intermediate product is then reacted with(c) the hydrocarbon polyene, in the presence of additional catalyst.

The reactions for forming the polymers and prepolymers of this inventioncan be promoted thermally or by the addition of a hydrosilation catalystor a free radical generator such as a peroxide or an azo compound.Hydrosilation catalysts include metal salts and complexes of Group VIIIelements. The preferred hydrosilation catalysts contain platinum, e.g.,bis(acetonitrile)platinum dichloride, bis(benzonitrile)platinumdichloride, platinum on carbon, platinum dichloride, platinum-divinylcomplexes, cyclooctadieneplatinum dichloride, dicyclopentadieneplatinumdichloride and chloroplatinic acid. The platinum catalyst is present inan amount of 0.0005% to 0.05% by weight of platinum, based on the weightof the monomers, preferably 0.002% to 0.05%, and most preferably 0.005%to 0.01%.

It is possible, by selection of reactants, reactant concentrations andreaction conditions, to prepare polymers exhibiting a broad range ofproperties and physical forms. Thus, it has been found possible toprepare tacky solids, elastomeric materials, and tough glassy polymers.

Generally, the ratio of carbon-carbon double bonds in the fullysubstituted cyclic polysiloxane or mixtures thereof with the hydrocarbonpolyene, to .tbd.SiH groups in the organosilicon compounds is in therange of 0.51:1 to 1.3:1, preferably 0.7:1 to 1.1:1, most preferably0.95:1 to 1.05:1.

The prepolymers are stable at room temperature for varying periods oftime, and cure upon reheating to an appropriate temperature, e.g., about100° to about 250° C. Frequently additional catalyst is added to theprepolymer prior to cure to further promote the reaction.

When preparing the polymers and prepolymers of this invention, thereaction speed and its accompanying viscosity increase can be controlledby use of low levels of a cure rate retardant (complexing agent), suchas N,N,N',N'-tetramethylethylenediamine, diethylenetriamine orphosphorus compounds, such as those described in "Phosphorus BasedCatalyst Retardants for Silicon Carbon Resin Systems", ResearchDisclosure 326103 (June 1991), which is incorporated by reference in itsentirety. The cure rate retardants are also useful to maintain thestorage stability and to control the viscosity profile of the prepolymeras described in European Patent Application 479,310 (Babcock et al.),which is incorporated by reference in its entirety.

Stabilizers (antioxidants) are useful to maintain storage stability andthermal oxidative stability. Suitable stabilizers include, for example,bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-(3,5-di-tert-butyl-4-hydroxybenzyl)butylpropanedioate(available as TINUVIN™ 144 from Ciba-Geigy Corp., Hawthorne, N.Y.), or acombination of octadecyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate (alsoknown as octadecyl 3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate)available as NAUGARD™ 76 from Uniroyal Chemical Co., Middlebury, Conn.,and bis(1,2,2,6,6-pentamethyl-4-piperidinyl sebacate), available asTINUVIN™ 765 from Ciba-Geigy Corp. Stabilizers and their use aredescribed in U.S. Pat. Nos. 5,025,048 and 5,118,735, which are bothincorporated by reference in their entirety.

An elastomer can be added to improve the toughness of the organosiliconpolymer-containing compositions of the present invention. Although anyelastomer can be added to impart toughness, hydrocarbon elastomers arepreferred for use in the present invention. Preferred areethylene-propylene-ethylidenenorbornene polymers having a molecularweight of from about 5500 to about 7000. Elastomers are generally usedin an amount of from about 0.5 to 20 weight %, preferably from about 3to about 12 weight % of the total composition. Elastomers can be addedto the monomers or to the prepolymer. Use of elastomers is described inU.S. Pat. No. 5,147,958 and European Patent Application 482,404 (Barnum& Brady), as well as "Organosilicon Compositions Containing HydrocarbonElastomers", Research Disclosure 33082 (October 1991), all of which areincorporated by reference in their entirety.

One or more flame retardants can also be added to the compositions ofthis invention. The flame retardant preferably comprises at least onemember selected from the group consisting of phosphorus-containingcompounds and halogen-containing compounds. Exemplary are ammoniumpolyphosphates, phosphazenes, phosphine oxides, phosphate esters,elemental red phosphorus, brominated alkyls, brominated diphenyl oxides,brominated polystyrenes, brominated bisphenol A's, andhexachlorocyclopentadiene derivatives. Use of flame retardants isdescribed in U.S. Ser. No. 07/839,610 (Babcock et al.), filed Feb. 211992, U.S. Pat. No. 5,298,536, which is incorporated by reference in itsentirety.

Fillers can also be added to the compositions of this invention. Typicalfillers include, for example, carbon black, vermiculite, mica,wollastonite, calcium carbonate, sand, glass spheres, glass beads,ground glass, waste glass, fused silica, fumed silica, synthetic silica,glass fibers, and glass flakes. Other useful fillers include the fiberreinforcements that are described in U.S. Pat. Nos. 4,900,779,4,902,731, 5,008,360 and 5,068,303, each of which is incorporated hereinby reference.

The polymers and prepolymers of this invention have excellent electricalinsulating properties and resistance to moisture. They are thereforewell suited for electronic applications, e.g., composites, adhesives,encapsulants, potting compounds and coatings. They are especially usefulin applications requiring high shear modulus, low coefficient of thermalexpansion and moderate glass transition temperature, for example, in themanufacture of printed circuit boards and high performance composites.

All parts and percentages in this specification are by weight unlessotherwise noted.

EXAMPLE 1

This example describes the preparation of a fully substitutedcyclotrisiloxane in which cyclization occurs after hydrolysis of theR'-substituted dichlorosilane in methyl ethyl ketone.

Dicyclopentadiene (DCPD) (200 g, 1.52 mol) and 2,332 μl (2.06 μl=10ppm/g resin, 30 ppm) of a platinum-divinyl complex (a vinyl-terminatedpolydimethylsiloxane/toluene solution supplied by Huls American), wereadded to a three-necked 500 ml round bottom flask equipped with acondenser and a dropping funnel. Dichloromethylsilane (177.4 g, 1.54mol) was added dropwise through the dropping funnel at room temperaturewith a magnetic stirrer. An exothermic reaction (2° C. increase) wasobserved. After addition, the temperature was raised to 45°-50° C. andthis temperature was maintained for three hours. The reaction mixturewas cooled to room temperature. Vacuum distillation of the mixture wascarried out using a Kugelrohr apparatus. The product, methyl(2,3dihydro-2-dicyclopentadienyl)-dichlorosilane (312.3 g, 82.8%), wascollected between 80° and 100° C. at a vacuum of 1 mm Hg.

An aqueous solution of methyl ethyl ketone (MEK) (7 g water in 150 mlMEK) was placed in a three-necked flask equipped with a condenser and adropping funnel. Methyl(2,3-dihydro-2-dicyclopentadienyl)-dichlorosilane (40 g, 0.16 mol) wasadded through the dropping funnel. After addition, the solution wasrefluxed for two hours. The residue was dissolved in ether and washedwith saturated sodium bicarbonate solution (100 ml) and distilled water(150 ml×4). The solution was dried over anhydrous magnesium sulfate. Thesolvent was then evaporated in vacuo, first by a Rotovap, then by aKugelrohr distillation apparatus at 80° C. under a vacuum of 1 mm Hg. Amixture of the fully substituted cyclic trisiloxane(1,3,5-tris(2,3-dihydro-2-dicyclopentadienyl)-1,3,5-trimethylcyclotrisiloxane)and the corresponding fully substituted cyclic tetrasiloxane wasobtained at 96% yield (30.0 g). The product was a colorless viscous oil,which turned to a white solid on standing. The ratio of cyclictrisiloxane to cyclic tetrasiloxane was 54/46 mol %.

Example 2

This example describes the preparation of a fully substitutedcyclotrisiloxane in which cyclization occurs after hydrolysis of theR'-substituted dichlorosilane in aqueous ether.

Methyl (2,3-dihydro-2-dicyclopentadienyl)-dichlorosilane (38.0 g, 0.15mol), prepared as described in Example 1, was added through a droppingfunnel to an aqueous solution of ether (8 ml of water in 150 ml ofether). After addition, the solution was refluxed for four hours. Thesolution was cooled to room temperature and washed with distilled water(100 ml), saturated sodium bicarbonate (100 ml), and distilled water(100 ml×4) in sequence. The organic layer was dried over anhydrousmagnesium sulfate. The solvent was evaporated in vacuo. The product wasa colorless viscous oil, which turned to a white solid on standing. Amixture of fully substituted cyclic trisiloxane(1,3,5-trimethylcyclotrisiloxane) and the corresponding fullysubstituted cyclic tetrasiloxane was obtained at 95% yield (28.0 g). Theratio of cyclic trisiloxane to cyclic tetrasiloxane was 90/10 mol %.

EXAMPLE 3

This example describes the preparation of a fully substitutedcyclotrisiloxane in which cyclization occurs after reaction of theR'-substituted dichlorosilane with t-butyl alcohol.

A solution of 32.0 g (0.44 mol) of t-butyl alcohol in 120 ml of hexanewas added to a three-necked flask equipped with a condenser and adropping funnel. Methyl (2,3-dihydro-2-dicyclopentadienyl)dichlorosilane (50 g, 0.20 mol), prepared as described in Example 1, wasadded through the dropping funnel. The reaction temperature wascontrolled below 15° C. by an external ice bath and by the rate ofaddition. The solution was washed with saturated sodium bicarbonatesolution (100 ml) and distilled water (100 ml×5) and then dried overanhydrous magnesium sulfate. The solvent was evaporated in vacuo using arotoevaporator and a Kugelrohr distillation apparatus in sequence. Amixture of the fully substituted cyclic trisiloxane(1,3,5-tris(2,3-dihydro-2-dicyclopentadienyl)-1,3,5-trimethylcyclotrisiloxane)and the corresponding fully substituted cyclic tetrasiloxane wasobtained at 75% yield (28.8 g). The product was a white solid. The ratioof cyclic trisiloxane to cyclic tetrasiloxane was 65/35 mol %.

EXAMPLE 4

This example describes the preparation of a fully substitutedcyclotrisiloxane in which cyclization occurs after reaction of theR'-substituted dichlorosilane with ZnO in ethyl acetate.

Bicyclo[2.2.1] heptenylmethyldichlorosilane was prepared by the methoddescribed in Example 1, using norbornadiene instead ofdicyclopentadiene.

Bicyclo[2.2.1] heptenylmethyldichlorosilane (30.0 g, 0.12 mole) wasadded dropwise to a mixture of 11.9 g (0.145 mole) of zinc oxide and 100ml of ethyl acetate at room temperature under a nitrogen atmosphere withagitation. The mixture was heated to reflux for five hours. The mixturewas cooled to room temperature and the white solid was filtered offthrough CELITE™ filter aid supplied by Manville Corp. The organicsolution was washed with brine (1×100 ml), saturated sodium bicarbonate(1×100 mol), and brine (3×100 ml) respectively. The solution was thendried over anhydrous magnesium sulfate and the solvent was evaporatedunder vacuum. A mixture of the fully substituted cyclic trisiloxane(1,3,5-trimethyl-1,3,5-trikis[5-bicyclo(2.2.1)heptenyl]cyclotrisiloxane)and the corresponding fully substituted cyclic tetrasiloxane wasobtained at 81% yield (18.5 g). The product was a viscous liquid, whichturned to a white solid on standing. The ratio of cyclic trisiloxane tocyclic tetrasiloxane was 60/40 mol %.

COMPARATIVE EXAMPLE 1

This example describes the preparation of a prepolymer and cured polymerfrom a polycyclic polyene and a methylhydrocyclosiloxane without a fullysubstituted cyclic polysiloxane.

Dicyclopentadiene (11.0 g), 10.4 g of1,3,5,7-tetramethylcyclotetrasiloxane (Huls American), and 0.15 ml of aplatinum-divinyl complex (Huls American PCO72, a xylene solutioncontaining 0.56% of Pt, 35 ppm) were added to a round bottom one-neckflask. Heating the mixture to 70° C. resulted in an exothermic reactionand formation of an organosilicon prepolymer. To this prepolymer wasadded 0.33 ml of PC072 (75 ppm) in portions, followed by 8.4 ml of asolution of diethylenetriamine cure rate retardant (DETA) (5% intoluene, 20 ppm). The solvent was evaporated under vacuum. The catalyzedprepolymer was then poured into a mold. The sample was cured at 170° C.for one hour and postcured at 240° C. for four hours. The cured samplewas a colorless and hazy solid. The shear modulus G' of the polymer was8.80×10⁹ dyne/cm² and was determined by dynamic mechanical analysisusing a Rheometrics mechanical spectrometer Model RMS-605. Thecoefficient of thermal expansion (CTE) of the polymer was 95.8 ppm/° C.between 60° to 100° C. and was determined by thermal mechanical analysis(TMA) using a DuPont TMA Analyzer Model 220 (see Table 1).

EXAMPLE 5

This example describes the preparation of a prepolymer in which apolycyclic polyene was first reacted with a methylhydrocyclosiloxane inthe presence of a catalyst and the reaction product was then reactedwith a fully substituted cyclic polysiloxane in the presence ofadditional catalyst.

Dicyclopentadiene (6.1 g), 10.95 g of1,3,5,7-tetramethylcyclotetrasiloxane, and 0.12 ml of a platinum-divinylcomplex (Huls American PC075, a vinyl-terminatedpolydimethylsiloxane/toluene solution containing 0.56% of Pt, 35 ppm)were added to a round bottom one-necked flask. Heating the mixture to70° C. resulted in an exothermic reaction and formation of anorganosilicon prepolymer.1,3,5-Tris(2,3-dihydro-2-dicyclopentadienyl)-1,3,5-trimethylcyclotrisiloxane(17.4 g) in 20 ml of toluene was added to the prepolymer, followed by0.65 ml of the platinum catalyst (total 110 ppm). The solvent wasevaporated under vacuum and the catalyzed prepolymer was poured into amold. The sample was cured at 170° C. for one hour and postcured at 240°C. for four hours. The cured sample was a colorless and hazy solid. Theshear modulus of the polymer was 1.10×10¹⁰ dyne/cm² by dynamicmechanical analysis. The CTE of the polymer was 91.6 ppm/° C. between60° to 100° C. (TMA) (see Table 1).

COMPARATIVE EXAMPLE 2

This example describes the preparation of a prepolymer and cured polymerfrom dicyclopentadiene and a methylhydrocyclosiloxane without the use ofa fully substituted cyclic polysiloxane.

Dicyclopentadiene (11.0 g), 10.0 g of1,3,5,7-tetramethylcyclotetrasiloxane (Huls American), and 0.13 ml of aplatinum-divinyl complex (Huls American PC072, a xylene solutioncontaining 0.56% of Pt, 30 ppm) were added to a round bottom one-neckflask. Heating the mixture to 70° C. resulted in an exothermic reactionand formation of an organosilicon prepolymer. To this prepolymer wasadded 0.30 ml of PC072 (70 ppm) in portions, followed by 8.4 ml of asolution of diethylenetriamine cure rate retardant (DETA) (5% intoluene, 20 ppm). The solvent was evaporated under vacuum and thecatalyzed prepolymer was poured into a mold. The sample was cured at170° C for one hour and postcured at 240° C. for four hours. The curedsample was a colorless and hazy solid. The shear modulus G' of thepolymer was 8.20×10⁹ dyne/cm² by dynamic mechanical analysis. Thecoefficient of thermal expansion (CTE) of the polymer was 102 ppm/° C.between 60° C. to 100° C. (TMA) (see Table 1)

EXAMPLE 6

This example describes the preparation of a prepolymer and cured polymerin which all of the components were added at the same time.

Dicyclopentadiene (40 g), 7.5 g of1,3,5,7-tetramethylcyclotetrasiloxane, 11.6 g of1,3,5-tris(2,3-dihydro-2-dicyclopentadienyl)-l,3,5-trimethylcyclotrisiloxane,and 0.14 ml of a platinum-divinyl complex (Huls American PC075, avinyl-terminated polydimethylsiloxane/toluene solution containing 0.56%of Pt, 30 ppm) were added to a round bottom one-necked flask. Heatingthe mixture to 70° C. resulted in an exothermic reaction and theformation of an organosilicon prepolymer. The same platinum catalyst(0.33 ml, 100 ppm) was added to the prepolymer. The solvent wasevaporated under vacuum and the catalyzed prepolymer was poured into amold. The sample was cured at 170° C. for one hour and postcured at 240°C. for four hours. The cured sample was a colorless and hazy solid. Theshear modulus of the polymer was 1.11×10¹⁰ dyne/cm² by dynamicmechanical analysis. The CTE of the polymer was 97.9 ppm/° C. between60° C. to 100° C. (TMA) (see Table 1).

The data from Comparative Examples 1 and 2 and Examples 5 and 6 aresummarized in the following table. The data indicate that the shearmodulus G' increases and the coefficient of thermal expansion (CTE)decreases for cured polymers made from fully substituted cyclicpolysiloxanes compared with polymers made without them.

                  TABLE 1                                                         ______________________________________                                                 DCPD/D.sub.3                                                                  (weight   PCO75   G' (× 10.sup.9)                                                                  CTE, ppm                                  Example  ratio)    (ppm)   (dynes/cm.sup.2)                                                                       (60-100° C.)                       ______________________________________                                        Comp. Ex. 1                                                                            1/0       110      8.80    95.8                                      Ex. 5    1/3       110     11.0     91.6                                      Comp. Ex. 2                                                                            1/0       100      8.2     102.0                                     Ex. 6    1/3       100     11.1     97.9                                      ______________________________________                                    

I claim:
 1. An organosilicon crosslinked polymer or crosslinkableprepolymer that is the hydrosilation reaction product of:(a) a cyclicpolysiloxane having the formula ##STR7## where R is a saturated,substituted or unsubstituted alkyl or alkoxy group or a substituted orunsubstituted aryl or aryloxy group, R' is a substituted orunsubstituted hydrocarbon group having at least one nonaromaticcarbon-carbon double bond that is reactive in hydrosilation, and n is 3,or 3 and 4, (b) at least one organosilicon compound having at least two.tbd.SiH groups selected from the group consisting of (1) cyclicpolysiloxanes and (2 tetrahedral siloxysilanes, and (c) at least onehydrocarbon polyene having at least two nonaromatic carbon-carbon doublebonds that are reactive in hydrosilation,said hydrosilation reactionbeing carried out in the presence of a, hydrosilation catalyst.
 2. Thepolymer or prepolymer of claim 1, wherein the hydrocarbon polyene (c) isa polycyclic polyene selected from the group consisting ofcyclopentadiene oligomers, norbornadiene dimer, bicycloheptadiene andits Diels-Alder oligomers with cyclopentadiene.
 3. The polymer orprepolymer of claim 2, wherein the polycyclic polyene is selected fromthe group consisting of dicyclopentadiene, tricyclopentadiene,tetracyclopentadiene, dimethanohexahydronaphthalene andmethyldicyclopentadiene.
 4. The polymer or prepolymer of claim 3,wherein the polycyclic polyene is dicyclopentadiene.
 5. The polymer orprepolymer of claim 3, wherein R in component (a) is a 1-10 carbon alkylgroup, R' is a polycyclic hydrocarbon group having at least onecarbon-carbon double bond that is reactive in hydrosilation, and (b) isa cyclic polysiloxane.
 6. The polymer or prepolymer of claim 4, whereinR in component (a) is a methyl group, R' is a dicyclopentadienyl or5-bicyclo[2.2.1]heptenyl group, and (b) is a cyclic polysiloxaneselected from the group consisting of1,3,5,7-tetramethylcyclotetrasiloxane;1,3,5,7,9-pentamethylcyclopentasiloxane;1,3,5,6,9,11-hexamethylcyclohexasiloxane and mixtures thereof.
 7. Aprocess for preparing a crosslinked polymer or a crosslinkableprepolymer comprising reacting:(a) a cyclic polysiloxane having theformula ##STR8## where R is a saturated, substituted or unsubstitutedalkyl or alkoxy group or a substituted or unsubstituted aryl or aryloxygroup, R' is a substituted or unsubstituted hydrocarbon group having atleast one nonaromatic carbon-carbon double bond that is reactive inhydrosilation, and n is 3, or 3 and 4, (b) at least one silicon compoundhaving at least two .tbd.SiH groups selected from the group consistingof (1) cyclic polysiloxanes and (2) tetrahedral siloxysilanes, and (c)at least one hydrocarbon polyene having at least two nonaromaticcarbon-carbon double bonds that are reactive in hydrosilation, in thepresence of a hydrosilation catalyst.
 8. The process of claim 7, whereinR in component (a) is a 1-10 carbon alkyl group, and R' is a polycyclichydrocarbon group having at least one carbon-carbon double bond that isreactive in hydrosilation; (b) is a cyclic polysiloxane, and (c) isselected from the group consisting of dicyclopentadiene,tricyclopentadiene, tetracyclopentadiene, dimethanohexahydronaphthaleneand methyldicyclopentadiene.
 9. The process of claim 8, wherein R incomponent (a) is a methyl group, and R' is a dicyclopentadienyl group ora 5-bicyclo[2.2.1]heptenyl group; (b) is a cyclic polysiloxane selectedfrom the group consisting of 1,3,5,7-tetramethylcyclotetrasiloxane;1,3,5,7,9-pentamethylcyclopentasiloxane;1,3,5,6,9,11-hexamethylcyclohexasiloxane and mixtures thereof, and (c)is dicyclopentadiene.
 10. A process for preparing a crosslinked polymeror a crosslinkable prepolymer comprising (1) reacting at least onesilicon compound having at least two .tbd.SiH groups selected from thegroup consisting of cyclic polysiloxanes and tetrahedral siloxysilanes,and at least one hydrocarbon polyene having at least two nonaromaticcarbon-carbon double bonds that are reactive in hydrosilation in thepresence of a hydrosilation catalyst to produce an intermediate reactionproduct, and then (2) reacting the intermediate reaction product with acyclic polysiloxane having the formula: ##STR9## where R is a saturated,substituted or unsubstituted alkyl or alkoxy group or a substituted orunsubstituted aryl or aryloxy group, R' is a substituted orunsubstituted hydrocarbon group having at least one nonaromaticcarbon-carbon double bond that is reactive in hydrosilation, and n is 3,or 3 and 4, in the presence of additional hydrosilation catalyst. 11.The process of claim 10, wherein the silicon compound in step (1) is acyclic polysiloxane, and the hydrocarbon polyene is selected from thegroup consisting of dicyclopentadiene, tricyclopentadiene,tetracyclopentadiene, dimethanohexahydronaphthalene andmethyldicyclopentadiene; R in the cyclic polysiloxane of step (2) is a1-10 carbon alkyl group and R' is a polycyclic hydrocarbon group havingat least one carbon-carbon double bond that is reactive inhydrosilation.
 12. The process of claim 11, wherein the silicon compoundin step (1) is a cyclic polysiloxane selected from the group consistingof 1,3,5,7-tetramethylcyclotetrasiloxane;1,3,5,7,9-pentamethylcyclopentasiloxane;1,3,5,6,9,11-hexamethylcyclohexasiloxane and mixtures thereof, and thehydrocarbon polyene is dicyclopentadiene; R in the cyclic polysiloxaneof step (2) is a methyl group and R' is a dicyclopentadienyl or a5-bicyclo[2.2.1]heptenyl group.
 13. A process for preparing acrosslinked polymer or a crosslinkable prepolymer comprising (1)reacting a cyclic polysiloxane having the formula: ##STR10## where R isa saturated, substituted or unsubstituted alkyl or alkoxy group or asubstituted or unsubstituted aryl or aryloxy group, R' is a substitutedor unsubstituted hydrocarbon group having at least one nonaromaticcarbon-carbon double bond that is reactive in hydrosilation, and n is 3,or 3 and 4, with at least one silicon compound having at least two.tbd.SiH groups selected from the group consisting of cyclicpolysiloxanes and tetrahedral siloxysilanes, in the presence of ahydrosilation catalyst to produce an intermediate reaction product, andthen (2) reacting the intermediate reaction product with at least onehydrocarbon polyene having at least two nonaromatic carbon-carbon doublebonds that are reactive in hydrosilation, in the presence of additionalhydrosilation catalyst.
 14. The process of claim 13, wherein R in thecyclic polysiloxane of step (1) is a 1-10 carbon alkyl group, and R' isa polycyclic hydrocarbon group having at least one carbon-carbon doublebond that is reactive in hydrosilation; the silicon compound is a cyclicpolysiloxane, and the hydrocarbon polyene is selected from the groupconsisting of dicyclopentadiene, tricyclopentadiene,tetracyclopentadiene, dimethanohexahydronaphthalene, andmethyldicyclopentadiene.
 15. The process of claim 14, wherein R in thecyclic polysiloxane of step (1) is a methyl group, and R' is adicyclopentadienyl or a 5-bicyclo[2.2.1]heptenyl group; the siliconcompound is a cyclic polysiloxane selected from the group consisting of1.3,5,7-tetramethylcyclotetrasiloxane;1,3,5,7,9-pentamethylcyclopentasiloxane;1,3,5.6.9,11-hexamethylcyclohexasiloxane and mixtures thereof, and thehydrocarbon polyene is dicyclopentadiene.
 16. The process of claim 7,wherein the ratio of carbon-carbon double bonds in (a) and (c) to.tbd.SiH groups in (b) is 0.7:1 to 1:1.
 17. The process of claim 10,wherein the ratio of carbon-carbon double bonds to .tbd.SiH groups is0.7:1 to 1.1:1.
 18. The process of claim 13, wherein the ratio ofcarbon-carbon double bonds to .tbd.SiH groups is 0.7:1 to 1.1:1.